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Equine Rhinopneumonitis

A highly contagious disease, equine viral
rhinopneumonitis is also known as viral abortion. As is inferred from the
name the disease can result in abortion following possible respiratory and
neurological problems. Equine viral rhinopneumonitis is caused by a strain
of the herpes virus called the equine herpes virus type 1 (EHV-1). Currently
there is no evidence to suggest that equine viral rhinopneumonitis affects
species other than the equine family. Symptoms include respiratory
infection and sometimes the central nervous system is adversely affected,
for example leading to paralysis. Generally a high temperature, lack of
appetite and nasal discharge is observed following infection. Those more
susceptible to infection are foals and young horses although horses of all
ages are able to catch the disease. The age of the infected horse also leads
to different levels of severity concerning the signs and symptoms. The
disease is usually transmitted via infected aerosol droplets if inhaled by
the horse. Due to the fact that the disease cannot be transferred to humans,
the disease is not known as zoonotic. Vaccinations are available to protect
against this disease though do not always provide complete protection.

Transmission

The virus which causes equine viral rhinopneumonitis is
transmitted via infected aerosol droplets inhaled by the horse. Contaminated
surfaces such as clothing, buckets, footwear and even hands can cause the
spread of the disease which means that even owners with just the one animal
can put their horse at risk. Some horses can even shed the virus without
showing any symptoms which is also a cause for concern. In addition,
transmission can occur following ingestion of infected faeces, nasal
discharge and saliva.

The herpes virus is able to survive for as long as two
months and so following infection strong disinfectants containing bleach or
ammonia should be used to destroy the virus on contaminated surfaces, thus
preventing further transmission. Any bedding that was present near or with
the infected horse should be gotten rid of and good ventilation is required
to dry out the stables.

Symptoms

The milder form of the disease includes a high
temperature, nasal discharge, a distinct difficulty in attempts to urinate
and a lack of appetite. The nasal discharge will be serous in appearance and
texture. Young horses usually recover if a secondary infection such as
pneumonia is not present. In some circumstances, equine viral
rhinopneumonitis can progress giving rise to an attack of the central
nervous system (CNS) which can result in uncoordinated gaits, the horse not
being able to stand up and even paralysis.

The symptoms and clinical signs of equine viral
rhinopneumonitis are more severe in younger foals where death can occur
within just one day. Mares can abort their unborn foetuses during the last
few months of pregnancy, usually between eight and eleven months, which can
have adverse economic implications. This is caused by respiratory problems
as the foetus no longer has an adequate supply of oxygen since it will have
been separated too early from the placenta.

Treatment and Prevention

Only supportive treatment can be given to the infected
horse as, unfortunately, there is simply no cure against equine
rhinopneumonitis. The horse should stop work and antibiotics are often
administered to prevent the possibility of bacteria causing what is called a
secondary infection.

Vaccinations are available against equine viral
rhinopneumonitis and are initially given to horses as young as three months
old and then the second dose given one month later. Following this, boosters
are normally given twice yearly to provide long term immunity although for
pregnant mares the schedule is a little different. They are vaccinated every
two months during pregnancy, with first commencing at around the fifth
month. Currently, the vaccine does not yet protect against the neurological
implications which may be a result of an infection of the virus. Competing
horses which travel a lot are strongly encouraged to be vaccinated.

Diagnosis and Prognosis

Following an observation of the signs and symptoms,
blood samples are taken and tested for the disease. Most cases recover but
in horses where paralysis and the inability to stand up is observed, the
prognosis is rarely good.

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